The invention is a process for esterifying terminal hydroxyl groups of a polyoxyalkylene compound comprising one or more oxyethylene units bearing on either carbon atom an alkoxy group represented by the formula --CH.sub.2 OR where R is tert.-butyl or tert.-amyl without removing a significant portion of said R groups.
In U.S. Pat. No. 3,519,559 (1970) polyoxyalkylene compounds similar to those employed in the instant process are reacted with polycarboxylic acids to prepare higher molecular weight polyesters. The only catalyst mentioned therein, in the specific examples of Table II, is p-toluenesulfonic acid (PTSA). In U.S. Pat. No. 3,840,606 dealkylation of tert.-butyl groups from polyoxyalkylene compounds similar to those employed herein is described as occurring in the presence of sulfonic acids under aqueous conditions and in U.S. Pat. No. 4,048,237 a similar reaction is described except under substantially anhydrous conditions.
In U.S. Pat. Nos. 4,003,961 and 4,092,339 at column 5 of each, esterification of the terminal hydroxyls of polyoxyalkylene compounds of this invention is described using acid anhydrides under temperatures of 30.degree.-90.degree. C. or, in the presence of bases, acyl halides, or at higher temperatures with carboxylic acids in the presence of acid catalysts and higher temperatures. It is noted that the presence of strong acids such as aryl sulfonic acids causes simultaneous dealkylation and esterification of the pendant tert.-butoxy groups. Organotin compounds are known to be esterification catalysts for other alcohol/acid reactants.